Compass, Magnetic Direct Reading, US Navy Mark IX
Here is an example of the WWII-era US Navy Aircraft Direct Reading Magnetic Compass Mark IX, as used in the seaplanes PBY Catalina and PBM Mariner Patrol Bombers.
The compass was illuminated electrically via bulb mounted in a small compartment over the compass itself. Inside the same compartment is access to the direction compensating screws, used to calibrate the compass.
This example is in reasonable condition for its age. The fluid is absent. Measures ~3.3 inches tall by ~5 inches wide and ~5 inches deep.